Translations:Introduction - Chapter 15/8/en

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These modes of description are related to one another, and each offers advantages in different types of applications. Because the characteristics of the entire system are contained in these functions, it is important to understand their properties. The essential properties of a transfer function are revealed by the location of its poles and zeros. If all the poles lie outside the unit circle (in the digital case) or within the left half-plane (in the analog case), the transfer function represents a stable causal system. All systems operating in real time are causal. All natural systems existing in long-run time are stable; otherwise, their output would keep increasing until finally it destroyed the system.